Al-Hujuraat 49:12

O you who believe, avoid much suspicion, for some suspicions are sin. Do not spy on one another, nor backbite one another. Would any of you like to eat the flesh of his dead brother[6]? You would surely abhor it. So fear Allah. Indeed, Allah is Accepting of Repentance, Most Merciful.

[6] Backbiting people is likened to eating their dead bodies, for the dead do not feel the pain if their flesh is eaten; likewise, the one who is absent does not feel the pain of backbiting. So, backbiting someone is like eating his flesh while he is dead.

O you who have believed, avoid much [negative] assumption. Indeed, some assumption is sin. And do not spy or backbite each other. Would one of you like to eat the flesh of his brother when dead? You would detest it. And fear Allāh; indeed, Allāh is Accepting of Repentance and Merciful.

12. O you who believe! Avoid much suspicion; indeed some suspicions are sins. And spy not, neither backbite one another. Would one of you like to eat the flesh of his dead brother? You would hate it (so hate backbiting)[2]. And fear Allâh. Verily, Allâh is the One Who forgives and accepts repentance, Most Merciful.

[2] (V.49:12).
a) Narrated Abû Hurairah رضي الله عنه Allâh’s Messenger صلى الله عليه وسلم said, "Beware of suspicion, for suspicion is the worst of false tales; and do not look for other’s faults, and do not do spying on one another, and do not practise Najsh* and do not be jealous of one another and do not hate one another, and do not desert (stop talking to) one another. And O Allâh’s worshippers! Be brothers!"(Sahih Al-Bukhari, Vol.8, Hadîth No.92).
b) Narrated Hudhaifah رضي الله عنه: I heard the Prophet صلى الله عليه وسلم saying, "A Qattât ** will not enter Paradise." (Sahih Al-Bukhari, Vol.8, Hadîth No.82).
c) Backbiting and the Statement of Allâh عز وجل: "And spy not, neither backbite one another."
Narrated Ibn ‘Abbâs رضي الله عنهما: Allâh’s Messenger صلى الله عليه وسلم passed by two graves and said, "Both of them (persons in the grave) are being tortured, and they are not being tortured for a major sin. This one used not to save himself from being soiled with his urine, and the other used to go about with calumnies (among the people to rouse hostilities, e.g., one goes to a person and tells him that so-and-so says about him such and such evil things)." The Prophet صلى الله عليه وسلم then asked for a green branch of a date-palm tree, split it into two pieces and planted one on each grave and said, "It is hoped that their punishment may be abated till those two pieces of the branch get dried." *** (Sahih Al-Bukhari, Vol.8, Hadîth No.78).
* Najsh means to offer a high price for something in order to allure another customer who is interested in the thing.
**A Qattât is a person who conveys disagreeable, false information from one person to another with the intention of causing harm and enmity between them.
***This action was a kind of invocation on the part of the Prophet صلى الله عليه وسلم for the deceased persons. [Fath Al-Bari, Vol.1, Page 332].

O ye who believe! Shun much suspicion; for lo! some suspicion is a crime. And spy not, neither backbite one another. Would one of you love to eat the flesh of his dead brother? Ye abhor that (so abhor the other)! And keep your duty (to Allah). Lo! Allah is Relenting, Merciful.